Fire extinguishing composition



Swiss 1 No Drawing. Application February 24, 1%4

Serial No. 412,401

Claims priority, application France January 3, 1952 2 Claims. (Cl. 252-8) For extinguishing fires, chiefly hydrocarbon fires, methyl bromide has been considered as the most desirable extinguishing agent since the time it was proposed to that p However the toxicity thereof has been responsible for many injuries.

It is an object of this invention to provide new fire extinguishing compositions which are less toxic but at least as and mostly more effective than methyl bromide.

I have found that fire extinguishing compositions particularly efiective for extinction of hydrocarbon fires such as air-crash fires can generally be obtained by associating partly brominated lower aliphatic hydrocarbons which have 1 to 3 carbon atoms and are liquid at ordinary temperature, methyl bromide being excluded with chloro fluoro derivatives of methane and ethane having a boiling point below l5 C., the partly brominated lower aliphatic hydrocarbons preferably being in major proportion.

Particularly effective are fire extinguishing compositions containing a major proportion of ethyl bromide orsymmetrical dibromo-ethane CH Br--CH Br or bromoform or of a mixture ethyl bromide, with bromoform, and a minor proportion of dichloro difluoro methane.

The use of dichloro difiuoro methane alone as a fire extinguishing agent would be hardly desirable in practice although the compound is a fairly good agent per se, because the boiling point thereof is 29 C. so that dichloro difiuoro methane is too readily vapourized to be effectively sprayed to a satisfactory distance. By admixing dichloro difluoro methane with a bromo compound as above defined, the individual drawbacks of the components fade away while the respective advantages thereof are mutually increased.

I have found that if employed jointly with chloro fluoro derivatives of methane and ethane having a low boiling point, particularly dichloro difiuoro methane and monochloro difiuoro methane, ethyl bromide and bromoform provide especially effective extinguishing compositions.

Ethyl bromide and bromoform are both more effective and less toxic than methyl bromide.

Ethyl bromide has a low freezing point (-119 C.) and a reasonably high boiling point (38.4" C.). While the lethal concentration of methyl bromide in air amounts to 23 mg. per litre, the lethal concentration of ethyl bromide is as high as 665 mg, i. e. about 28 times greater. The efiectiveness of ethyl bromide as measured in tests employing n-heptane as a fuel is 1.36 times that of methyl bromide.

However, where employed alone ethyl bromide is likely to show erratic perfomances and might then be judged as having an inferior effectiveness as compared with methyl bromide. Curiously enough, I found that where ethyl bromide is employed jointly with dichloro difiuoro methane, the mixtures show regular performances definitely better than those obtained with methyl bromide associated with dichloro difluoro methane. Bearing in 2,818,382 Patented Dec. 31

mind that dichloro difluoro methane is substantially devoid of toxicity, it will be realized that fire extinguishing compositions consisting of ethyl bromide and dichloro difluoro methane are highly desirable.

Bromoforrn or tribromo methane CHBr has a high boiling point (150.5" C.) and a particularly high specific gravity (2.902). The vapours thereof are heavy and have a tendency to spread say on the surface of ignited fuel pools. Such a beneficial property is the more valuable as bromoform is a fire extinguisher still more efiiective than ethyl bromide. Although it is more toxic than ethyl bromide, bromoforrn is far less toxic than methyl bromide so that it is safer to handle. Furthermore owing to the presence of non-toxic dichloro difiuoro methane in fire extinguishing compositions according to my invention, the toxicity of mixtures containing bromoform alone as a partly brominated hydrocarbon component is reasonably low.

Having a high boiling point, bromoform is not readily vapourized and if it is darted alone on a burning pool of hydrocarbon it impinges the pool in liquid condition and splashes so that it is difiicult to effect extinction. By adding dichloro difiuoro methane thereto according to my invention, the boiling point is depressed, vapourization of brornoform is favoured and consequently the drawback inherent in splashing is removed.

It is desirable in practice to associate with dichloro difluoro methane, mixtures of ethyl bromide and bromoform in various relative proportions, the compositions having a high content of ethyl bromide as compared with the bromoform content being desirable where a particularly low toxicity is required while those having a low content of ethyl bromide as compared with the bromoform content are desirable for a relatively greater efficieney.

Symmetrical dibromo ethane CH Br-CI-I Br is also desirable for association with chloro fluoro lower aliphatic hydrocarbon of the type specified, as it' is an effective extinguishing agent and the addition thereto of a chloro fluoro lower aliphatic hydrocarbon, particularly dichloro difluoro methane, depresses its freezing point which is relatively high (+10 C.) and its boiling point which is as high as 132 C. Dibromo ethane is more toxic than ethyl bromide but definitely less toxic than methyl bromide. I

Instead of the specific partly brominated lower aliphatic hydrocarbons above mentioned or in admixture therewith, fire extinguishing compositions in accordance with this invention may comprise methylene bromide (or dibromo methane), ethylene bromide (or vinyl bromide), asymmetrical dibromo ethane, propyl bromide or iso-propyl bromide.

While dichloro difiuoro methane is preferred by reason of its low cost, other chloro fluoro derivatives of methane and ethane having a boiling point below 15 C. may also be employed in my fire extinguishing compositions, particularly monochloro difiuoro methane.

Generally speaking, the proportion of chloro fluoro lower aliphatic hydrocarbon as above defined, particularly dichloro difiuoro methane ranges from 10 to 50 percent by weight, the best proportion varying according to the nature of the partly brominated lower aliphatic hydrocarbon or hydrocarbon associated therewith. As an average, proportions around 30 percent by weight are preferred as will be apparent from the following statements.

Binary mixtures of a very high extinguishing effectiveness are those containing from 20 to 50 parts by weight of dichloro difluoro methane, the remainder being bromoform. Binary mixtures having a little lower effectiveness but a very low toxicity are those containing 15 to 45 parts by weight of dichloro difiuoro methane, the remainder being ethyl bromide. Mixtures consisting of about one third by weight 'of di-chloro difiuoro methane and .two thirds by weight of ethyl bromide have been widely employed and found veryeffective.

By admixing 'bromoform with ethyl bromide in various relative proportions and associating the mixtures with dichloro difiuoro methane, a wide gamut of effective fire extinguishiugcompos'itions is available. The proportion of dichloro difiuoro methane in such compositions preferably ranges from L to 40 parts by weight, a greater or with 'bromoform and dichloro difiuoro methane are substantially the same as with ethyl bromide.

Monochloro difiuoro methane may be substituted for dichloro difiuoro methane, the proportion thereof in the compositions being the same.

In tests of various media for extinction of crash-fires, my preferred compositions containing one third by weight of dichloro difiuoro methane together with two thirds by weight of ethyl bromide and equal parts by weight of dichloro difiuoro methane, bromoform and ethyl bromide respectively proved to be the most eflicient agents, in particular definitely more efiicient than compositions containing methyl bromide in association with a propellant.

One test was made with a mock-up of an aircraft wing flooded with a mixture of kerosene and aircraft gasoline, the running fuel having been allowed to burn for 30 seconds'before the attack was made. Another test was eft'ected with a pool of 300 litres of the same fuel floating on an area of 400 sq. meters filled with water, the

fire ignited at several points having been allowed 30 seconds of free burning before the attack signal was given.

Marks were given to the competitors in consideration of various factors including .time taken for extinction, amount of medium expended and risk taken by each competitor, the lower the marks, the more efiicient the 4 media. My first mentioned composition was awarded 1886, my second mentioned composition 1168 and the composition containing methyl bromide 4710.

it should be understood that carrying my invention into effect it is desirable to arrange that the partly brominated hydrocarbon or hydrocarbons impinge on the fire to be extinguished as a suspension of minute liquid particles in the chloro .fluoro compound propellent.

Consequently my invention may be carried into effect by spraying a previously prepared extinguishing composition as above 'defined, as well as spraying the liquid, partly brominated hydrocarbon or hydrocarbons indicated by means of or dispersing the same into a stream of the chloro fluoro compound as a propellent. As the partly brominated hydrocarbon or jihydrocarbons are thus carried as very minute droplets, they can display a full activity owing to the large area they expose and are less easily swept away by wind or by gas streams rising from the fire, than methyl-bromide is.

It is pointed out that the partly brominated hydrocarbons I employ and out of which methyl bromide excluded, may be defined as organic compounds consisting of carbon, hydrogen and bromine, which are lower aliphatic hydrocarbons having no more than 3 carbon atoms, wherein bromine is substituted for a portion of the hydrogen atoms thereof and each bromine-bearing carbon atom bears no more than two hydrogen atoms.

This application is a continuation-in-part of my abandoned patent application Serial No. 327,680 of December 23, 1952.

What I claim is:

1. A fire extinguishing composition which is a mixture of 10-40 parts ,by weight of a chloro-difiuoro methane having not less than one, no more than two chlorine atoms with 60 parts by weight of a mixture of bromoform and ethyl bromide.

2. A fire extinguishing composition which consists of a mixture of approximately equal parts by weight of dic'hloro difiuoro methane, bromoform and ethyl bromide.

References Cited in the file of this patent UNITED STATES PATENTS 2,021,981 Bichowsky Nov. 26, 1935 2,569,979 Durfee et a1. Oct. 2, 1951 FOREIGN PATENTS 802,043 France Aug. .25, v1936 878,854 France Feb. 8, 1943 464,026 Canada Mar. 28, 1950 

1. A FIRE EXTINGUISHING COMPOSITION WHICH IS A MIXTURE OF 10-40 PARTS BY WEIGHT OF A CHIORO-DIFFUORO METHANE HAVING NOT LESS THAN ONE, NO MORE THAN TWO CHLORINE ATOMS WITH 90-60 PARTS BY WEIGHT OF A MIXTURE OF BROMOFORM AND ETHUL BROMIDE. 